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Journal of Pediatric Gastroenterology & Nutrition:
doi: 10.1097/MPG.0b013e3182650a4d
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Abnormal Gut Integrity Is Associated With Reduced Linear Growth in Rural Malawian Children

Weisz, Ariana J.*; Manary, Micah J.; Stephenson, Kevin*; Agapova, Sophia*; Manary, Faith G.*; Thakwalakwa, Chrissie; Shulman, Robert J.§; Manary, Mark J.*

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Author Information

*Department of Pediatrics, Washington University, St Louis, MO

School of Medicine, University of California San Diego, La Jolla, CA

Department of Community Health, College of Medicine, University of Malawi, Blantyre, Malawi

§Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX.

Address correspondence and reprint requests to Dr Mark Manary, St Louis Children's Hospital, One Children's Place, St Louis, MO 63110 (e-mail: manary@kids.wustl.edu).

Received 9 April, 2012

Accepted 17 June, 2012

This work was supported by the Hickey Family Foundation, the University of Malawi, and the USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital. The contents do not necessarily reflect the views or policies of the USDA, nor does mention of trade names, commercial products, or organizations imply endorsement by the US government.

The authors report no conflicts of interest.

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Abstract

ABSTRACT: The aim of the present study was to investigate the relation of environmental enteropathy, as measured by the dual sugar absorption test, to linear growth faltering in 2- to 5-year-old Malawian children. Dietary quality, food insecurity, anthropometry, and site-specific sugar testing were measured in 418 children, and anthropometry was reassessed 3 months later. A linear regression model predicting linear growth was created. Better growth was associated with less urinary lactulose excretion, more clean water usage, not sleeping with animals, and no previous history of malnutrition. Eighty-seven percent of children studied demonstrated evidence of environmental enteropathy. In conclusion, abnormal gut integrity is associated with reduced linear growth in a population of rural African preschool-age children.

Despite numerous nutrition support programs and infectious disease interventions, a reduction in linear growth (stunting) in children remains a prevalent public health problem (1). Stunting, a height-for-age z score (HAZ) <−2, affects an estimated 32% of children younger than 5 years in the developing world (1). Growth faltering among these children is not entirely explained by inadequate nutrition or acute infection (1–3). Environmental enteropathy (EE), an asymptomatic, diffuse villous atrophy of the small bowel associated with T-cell inflammatory infiltration and reduced intestinal integrity, is present in 20% to 80% of seemingly healthy, poor individuals living in the developing world (4–7). This damage promotes a chronic inflammatory state and reduces intestinal nutrient absorption, potentially contributing to malnutrition and poor growth.

EE can be assessed with a dual-sugar permeability test, in which mannitol and lactulose are consumed under controlled conditions and quantified in subsequent urine collection (7–9). Elevated lactulose excretion and/or reduced mannitol excretion reflect increased permeability of the gut mucosa and reduced surface area (10). Although studies have shown that increased permeability and/or surface area correlates with stunting in infants and toddlers, whether this relationship exists in older preschool children has not been described. We hypothesized that despite their greater resistance to environmental stressors compared with infants and toddlers, older children also would be at risk for stunting related to EE as reflected by increased gut permeability.

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METHODS

A total of 418 2- to 5-year-old children were recruited from 5 rural subsistence farming areas in southern Malawi in June and July of 2011 from a population enrolled in a gut microbiome study (11). These children were originally recruited because they were twins born in proximity to one of the surveillance sites, consuming a diet primarily of maize and legumes and had growth monitored every 2 to 3 months since birth. Exclusion criteria included any chronic debilitating illness, including known HIV infection or obvious congenital abnormalities, evidence of acute malnutrition, and a recent history or present case of diarrhea or hematochezia. The study was approved by the College of Medicine research ethics committee of the University of Malawi, the Washington University Human Research Protection Office, and the Baylor College of Medicine human investigations review board. Written and oral consent, as well as information regarding each child's household, hygienic practices, and recent health, were obtained at enrollment. Weight was measured using an electronic scale to the nearest 5 g. Length was measured to the nearest 0.5 cm using a canvas mat or the nearest 0.2 cm using a rigid length board. Mid-upper arm circumference was measured with a standard insertion tape to the nearest 0.2 cm. Edema was assessed, and household food insecurity and individual dietary diversity scores were measured using adapted versions of the indicator guides provided by Food and Nutrition Technical Assistance Project (12,13). Approximately 3 months after their initial visit, additional anthropometric measurements and health history were collected.

Caregivers were directed not to feed the child for 12 hours before participation. Children were given the nonmetabolized sugars, lactulose (5 g) and mannitol (1 g), dissolved in 100 mL of water. Urine was then collected for 4 hours. Ten milligrams of merthiolate was added to limit bacterial degradation of the sugars. Children were encouraged to drink water to facilitate urination and mothers were instructed not to breast-feed their children during this time. The total urine volume was measured and a 4-mL aliquot was transferred into a cryovial, flash frozen in liquid nitrogen, and transported at −80°C to Baylor College of Medicine.

The concentrations of lactulose and mannitol in the urine specimens were then analyzed by high-performance liquid chromatography as previously described (14). The assays are sensitive to 1-μg/mL lactulose and mannitol, and the coefficient of variation is ≤5% (14).

Anthropometric indices based on the World Health Organization's 2006 Child Growth Standards were calculated using Anthro version 3.1 (WHO, Geneva). The lactulose:mannitol ratio (L:M) and urinary excretion of lactulose and mannitol (as percentage of dose administered) were calculated. An L:M ratio ≥0.10 was defined as abnormal (14). Change in HAZ was compared between the children divided approximately into quartiles defined by the L:M and lactulose excretion. Comparisons of the means of each quartile were made using the Tukey-Kramer test.

Nonparametric bivariate correlations between change in HAZ and the demographic, sanitation, anthropometric, and gut function and integrity characteristics were calculated. Spearman correlation coefficients with a level of statistical significance <0.20 were used in linear regression modeling to determine the best predictors of linear growth. Backward linear regression modeling using change in HAZ as the dependent variable was then conducted (SPSS for Windows, version 20, SPSS Inc, Chicago, IL), eliminating terms with P > 0.10.

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RESULTS

A total of 418 children completed the study (Table 1), of which 364 (87%) had a L:M suggestive of EE. Change in HAZ was associated with greater lactulose excretion, but not increased L:M (Fig. 1).

Table 1
Table 1
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Figure 1
Figure 1
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Urinary lactulose excretion, initial weight-for-height z score, initial HAZ, the number of bicycles in the home, the presence of animals sleeping in the home, the times per day clean water was brought to the home, and whether the child had previously been treated for malnutrition were placed into the linear regression model. The linear regression model to predict change in HAZ (r2 = 0.52, F = 54.2, P < 0.001) found that urinary lactulose excretion, among other factors, was a predictor of linear growth (Table 2).

Table 2
Table 2
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DISCUSSION

Most of the rural Malawian children selected for study had evidence of EE and abnormal gut integrity that was associated with reduced linear growth. The study is limited in that these study children were not surveyed for acute infectious episodes during the period in which growth was measured. Acute infections are likely to affect linear growth substantially in that they create a short-term inflammatory state associated with catabolic metabolism. The study population is typical of rural subsistence farmers in southern and eastern Africa, and thus these data should be used with caution when considering urban populations or populations outside of sub-Saharan Africa.

Other studies that have examined the relation between gut integrity and linear growth have found correlations between EE, as determined by dual-sugar absorption testing, and HAZ (8,9). A study in Nepal found that the lactulose:creatinine ratio explained 9% of the height deficit during a 7-month period in both “squatter” and middle-class populations of 3- to 18-month-old children (9). Degree of increase in the mannitol excretion, but not lactulose, has also been positively correlated with change in body weight and weight-for-length z score during a 3-month period in malnourished Bangladeshi children ages 6 to 24 months (15). In Gambian children ages 2 to 15 months, 43% of observed growth faltering could be explained by the L:M, but lactulose excretion alone was not correlated with growth outcomes (5,7). Differences in the pattern of the perturbation of the mannitol and lactulose excretion and L:M between different populations may represent different insults to the children's gastrointestinal mucosa mediated by nutritional status, age, or environment. Our study is the first in older preschool children to describe this association.

EE, although asymptomatic, has been found to be associated with growth faltering (10), diarrhea (14), and kwashiorkor (16). Stunting has been associated with lower school performance and decreased adult physical productivity (17). It has been hypothesized that poor hygiene and living in a contaminated environment can lead to or exacerbate EE (1,6). Further research is needed to determine the etiology of EE to develop appropriate interventions.

The high prevalence of EE found in this population is similar to that found in young children in other rural Malawian villages (14). The analyses highlight the importance of EE to growth in rural African children. It is interesting to note that neither maternal education nor socioeconomic status were significant predictors of linear growth, although this population had a limited variability in both of these parameters. The pervasiveness of EE in this population and its association with reduced linear growth demonstrate the importance of further investigation into appropriate and successful interventions for ameliorating EE.

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REFERENCES

1. Humphrey JH. Child undernutrition, tropical enteropathy, toilets and handwashing. Lancet 2009; 374:1032–1035.

2. Adu-Afarwuah S, Lartey A, Brown KH, et al. Randomized comparison of 3 types of micronutrient supplements for home fortification of complementary goods in Ghana: effects on growth and motor development. Am J Clin Nutr 2007; 86:412–420.

3. Poskitt EME, Cole TJ, Whitehead RG. Less diarrhoea, but no change in growth: 15 years’ data from three Gambian villages. Arch Dis Child 1999; 80:115–120.

4. Menzies IS, Zuckerman MJ, Nukajam WS, et al. Geography of intestinal permeability and absorption. Gut 1999; 44:483–489.

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6. Kelly P, Menzies I, Crane R, et al. Responses of small intestinal architecture and function over time to environmental factors in a tropical population. Am J Trop Med Hyg 2004; 70:412–419.

7. Lunn PG, Northrop-Clewes CA, Downes RM. Intestinal permeability, mucosal injury, and growth faltering in Gambian infants. Lancet 1991; 338:907–910.

8. Goto R, Mascie-Taylor CGN, Lunn PG. Impact of intestinal permeability, inflammation status and parasitic infection on infant growth faltering in rural Bangladesh. Br J Nutr 2009; 101:1509–1516.

9. Panter-Brick C, Lunn PG, Langford RM, et al. Pathways leading to early growth faltering: an investigation into the importance of mucosal damage and immunostimulation in different socio-economic groups in Nepal. Br J Nutr 2009; 101:558–567.

10. Lunn PG. The impact of infection and nutrition on gut function and growth in childhood. Proc Nutr Soc 2000; 59:147–154.

11. Yatsunenko T, Rey FE, Manary MJ, et al. Human gut microbiome viewed across age and geography. Nature 2012;486:222–7.

12. Coates J, Swindale A, Bilinsky P. Household Food Insecurity Access Scale (HFIAS) for Measurement of Household Food Access: Indicator Guide. Washington, DC: Food and Nutrition Technical Assistance Project, Academy for Educational Development; 2007.

13. Swindale A, Bilinsky P. Household Dietary Diversity Score (HDDS) for Measurement of Household Food Access: Indicator Guide. Washington, DC: Food and Nutrition Technical Assistance Project, Academy for Educational Development; 2006.

14. Trehan I, Shulman RJ, Ou CN, et al. A randomized, double-blind, placebo-controlled trial of rifaximin, a nonabsorbable antibiotic, in the treatment of tropical enteropathy. Am J Gastroenterol 2009; 104:2326–2333.

15. Hossain MI, Nahar B, Hamadani JD, et al. Intestinal mucosal permeability of severely underweight and nonmalnourished Bangladeshi children and effects of nutritional rehabilitation. J Pediatr Gastroenterol Nutr 2010; 51:638–644.

16. Brewster DR, Manary M, Menzies I, et al. Intestinal permeability in kwashiorkor. Arch Dis Child 1997; 76:236–241.

17. Victora CG, Adair L, Fall C, et al. Maternal and child undernutrition: consequences for adult health and human capital. Lancet 2008; 371:340–357.

Keywords:

environmental enteropathy; intestinal integrity; lactulose mannitol test; linear growth

Copyright 2012 by ESPGHAN and NASPGHAN

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